/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.ignite.internal.processors.hadoop.v1;

import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.ignite.IgniteCheckedException;
import org.apache.ignite.internal.processors.hadoop.HadoopJob;
import org.apache.ignite.internal.processors.hadoop.HadoopTaskCancelledException;
import org.apache.ignite.internal.processors.hadoop.HadoopTaskContext;
import org.apache.ignite.internal.processors.hadoop.HadoopTaskInfo;
import org.apache.ignite.internal.processors.hadoop.HadoopTaskInput;
import org.apache.ignite.internal.processors.hadoop.v2.HadoopV2TaskContext;

/**
 * Hadoop reduce task implementation for v1 API.
 */
public class HadoopV1ReduceTask extends HadoopV1Task {
    /** {@code True} if reduce, {@code false} if combine. */
    private final boolean reduce;

    /**
     * Constructor.
     *
     * @param taskInfo Task info.
     * @param reduce {@code True} if reduce, {@code false} if combine.
     */
    public HadoopV1ReduceTask(HadoopTaskInfo taskInfo, boolean reduce) {
        super(taskInfo);

        this.reduce = reduce;
    }

    /** {@inheritDoc} */
    @SuppressWarnings("unchecked")
    @Override public void run(HadoopTaskContext taskCtx) throws IgniteCheckedException {
        HadoopJob job = taskCtx.job();

        HadoopV2TaskContext ctx = (HadoopV2TaskContext)taskCtx;

        JobConf jobConf = ctx.jobConf();

        HadoopTaskInput input = taskCtx.input();

        HadoopV1OutputCollector collector = null;

        try {
            collector = collector(jobConf, ctx, reduce || !job.info().hasReducer(), fileName(), ctx.attemptId());

            Reducer reducer;
            if (reduce) reducer = ReflectionUtils.newInstance(jobConf.getReducerClass(),
                jobConf);
            else reducer = ReflectionUtils.newInstance(jobConf.getCombinerClass(),
                jobConf);

            assert reducer != null;

            try {
                try {
                    while (input.next()) {
                        if (isCancelled())
                            throw new HadoopTaskCancelledException("Reduce task cancelled.");

                        reducer.reduce(input.key(), input.values(), collector, Reporter.NULL);
                    }
                }
                finally {
                    reducer.close();
                }
            }
            finally {
                collector.closeWriter();
            }

            collector.commit();
        }
        catch (Exception e) {
            if (collector != null)
                collector.abort();

            throw new IgniteCheckedException(e);
        }
    }
}